If you are going to be into the case:
Several times a week: tack weld grade 8 nuts or tapped inserts to the back.... consider buying a box of nylon screws so they wear out instead.
Several times a month: braze, solder or epoxy nuts on the back, or use the speed clips or similar.
A time or two a year, but it's about done now: run solder into the holes, or solder dip the screws. Also if aluminum foil duct tape available, small patches could be cut or punched, put over the outside of hole, allowing about the same diameter as hole all round to have a grip, then poke the hole through from outside with a pencil or pen or awl so it pushes into the hole, then screw into that. If you don't have that kind of duct tape, then cut tinfoil pie pans for patches and attach them with minimum amount of Uhu, Bostick, rubber cement type stuff and poke through the same when glue set.
Also a skilled metalworker can peen the holes a little bit closed to retap. Or you can take hours per hole doing it very carefully with a punch, just collapsing in the edges slightly.
Unicorn herding operations are proceeding, but all the totes of hens teeth and barrels of rocking horse poop give them plenty of hiding spots.